How Does My Car's Steering and Suspension (SAS) System Work?

For many car owners experiencing mechanical problems, it's comforting to know that someone who is trained and skilled in auto repair is on the job. That's why people come to see us at Sun Auto Service centers in the first place. However, we know some of our clients are curious about how everything works and why we suggest certain repairs after our diagnostic process. That's why we put together this overview of a car steering and suspension (SAS) system.

Steering and Suspension

Some components are part of both systems, but “divide and conquer” is the best strategy for understanding these essential parts of your ride. Your SAS system can be split into two general categories. The steering side is a complex chain that includes levers, joints, bushings, and conversion devices. It helps you control where you're going. The car suspension part uses hydraulics, struts, and springs of various configurations to locate your wheels and keep your vehicle at an appropriate ride height.

Staying in Control: Your Steering System

If you've ever experienced steering problems, you've probably heard the terms “rack and pinion” or “parallelogram” mentioned. These are the systems at the heart of many contemporary steering systems. Here's a brief explanation of how each of them works.

Rack and Pinion

Turn your steering wheel, and you're essentially rotating a pinion. This rotational force moves a rack, which causes your wheels to angle in one direction or another. Here's a visualization: The rack is a piece of metal with teeth like you'd get if you took the outer rim of a gear and laid it out flat in a line. The pinion is a circular gear that fits the teeth of the steering rack. As the pinion turns in place, the rack is forced to move from side to side. You have tie rods and control arms connecting this central shaft to the steering knuckles. When you move your wheel, it pulls the steering knuckles back and forth to the desired angles, allowing you to control the direction of your car or truck.

Pitman Arm and Power Steering System

The other popular type of steering design is known as parallelogram steering. Don't worry, you're not going to have to solve for “x” here. The term refers to the way all the joints and levers work together, forming a shape that mirrors the angles of your wheels as you steer. Some of the key components of this design are the power steering pump, Pitman arm, idler arm, and center link. The last three are metal parts that make up the famous parallelogram, but we'll go into more detail about that when we start talking about common steering issues.

A Smooth Ride: Your Suspension

There are so many different designs when it comes to suspensions that it's usually better to come into the shop and get some specific answers about your vehicle. There are many terms and designs. Independent suspension, dependent suspension, MacPherson struts, double wishbone, multi-link and semi-trailing arm are just a few. General information just isn't going to cut it. That said, models in a given class tend to have some similarities in their suspension systems.

Take the 2009 Ford F-150 truck suspension system as an example. This truck has an independent front suspension, meaning each wheel moves up and down by itself. This design helps you maintain control if you hit bumps and dips, and it keeps the ride smooth over rough terrain. Ford did this by using double wishbone arms and a shock absorber surrounded by a coil spring. The rear wheels are on a dependent suspension: a fixed axle with wheels located by sturdy leaf springs (long strips of spring metal layered one over the other). The overall result is a smooth ride and solid towing capacity. You can see similar configurations in other trucks, such as in the Chevy Silverado truck.

Identifying Steering or Suspension Issues

With all that in mind, it's pretty simple to figure out potential causes for some annoying and dangerous mechanical symptoms. Does your car seem to want to drive itself? It's probably a broken connection to your Pitman arm, throwing off your whole steering linkage. Is there vibration coming up through the steering wheel? You're probably looking at worn-out bushings or joints. Are you losing height, ride quality or control over bumps? That sounds like a problem with your suspension. There are no computer diagnostics available for these systems (with the exception of the power steering parts), so take your vehicle to the experienced technicians at Sun Auto Service. We'll look forward to seeing you at your local service center.